In January 2013, Winter Haven construction worker Michael Murray’s phone began ringing. On the other end, an automated message from national student loan provider Sallie Mae, which sometimes asked for his Social Security number when he would call back, claiming he owed money for a student loan.

They don’t know until months and months later that—wait a minute, these guys are not going to stop.

Murray attempted to take care of the matter himself, eventually getting through to a manager through an alternate phone line.

“He called up the person, said ‘you have the wrong number, you have the wrong person, I don’t owe you any money,’” Howard told Tampa’s 10 News online, “and they said ‘okay,’ then they called back the very next day.”

After hundreds of calls spanning four months, Murray, with Howard’s help, decided to file a lawsuit in federal court to put an end to the over-the-phone harassment over a non-existent debt.

“A lot of people think they just got one or two phone calls and they’re just going to stop,” Howard said. “They don’t know until months and months later that—wait a minute, these guys are not going to stop.”

According to Howard, founder of Morgan & Morgan’s Consumer Protection department, a robo dialer may call two million or more phone numbers a day, regardless of whether the person on the other end actually owes a debt.

“They don’t know if it’s not the right number, and they don’t care. They don’t check because they don’t care,” Howard explained. “They’re making a lot of money so they’re going to keep calling.”

If you’re being continually harassed by robocallers claiming you owe money, there are a few steps you can take to protect yourself. If immediately hanging up on the robocallers does nothing, you can register with the Federal Trade Commission’s “Do Not Call” registry. If that doesn’t put an end to the harassment, keep a log of your interactions with the robocaller, including the name of the company, their address and phone number and the names and titles of any managers to whom you may speak. If this fails, it may be time to contact a debt harassment attorney.